1) Field of the Invention
The present invention relates to a technology for accurately detecting quantity of waste developer collected in a container.
2) Description of the Related Art
Japanese Patent Application Laid-Open No. 11-282322, for example, discloses collection of waste developer in an electro photographic type image formation apparatus such as a copying machine or a printer. After a latent image formed on the photoreceptor is developed by developer and before the image is transferred onto a paper, extra developer (hereinafter, “waste developer”) remaining on the photoreceptor is scrapped using a cleaning apparatus and collected into a container (hereinafter, “collection container”). When the waste developer in the collection container exceeds a certain quantity, a warning that the collection container is full is displayed on an operation display section. When such a warning is displayed, a service person or someone around the device throws away the waste developer in the collection container and thus empties the collection container.
Thus, it is required to decide whether the waste developer in the collection container has exceeded the certain quantity. Japanese Patent Application Laid-Open No. 9-114225, for example, discloses how to detect the quantity of the waste developer in the collection container. This publication discloses two methods; a weight detection method and a time management method. In the weight detection method, a spring takes the weight of the collection container, a sensor detects amount of compression of the spring, and when the amount of compression exceeds a certain level, it is decided that the collection container is full with the waste developer. In the time management method, a controller counts the total operating time of a driving device that drives an arrangement for conveying the waste developer to the collection container, and when the operating time of the driving device exceeds a certain value, it is decided that the collection container is full with the waste developer.
However, the methods disclosed in the Japanese Patent Application Laid-Open No. 9-114225 have, for example, following problems. There is a great variation in the compression of the spring, and therefore, with the superposition detecting method it is difficult to detect the quantity of the waste developer accurately. The spring that takes the weight of the collection container makes the attachment and detachment of the collection container difficult. Moreover, the quantity of the waste developer produced differs according to types and sizes of the paper, the contents to be printed, and even the environmental conditions, therefore, the time management method, in which the quantity of the waste developer is estimated based on only the operating time, does not give accurate results.